What worried me is the discrepancy between reported fps and tbr in the original stream, also of note was the large quantity of the dropped frames - nearly half of them.

And indeed, while the original material had FPS of roughly 26, the converted file displayed FPS of 15, hence the dropped frames, though I did not specify -r option. And the difference in FPS is clearly visible by naked eye.

Expected: I expected ffmpeg to preserve the FPS of the original material in the absence of -r option.